1. Field of the Invention
This invention pertains to the field of capacitor chips and machinery that loads them into holders or masks for conveying them through various treatment processes. More particularly, this invention is a computer-driven combination of elements that ensures the chips are not loaded askew or in the wrong size masks such that they, or various parts of the equipment, suffer damage.
2. Description of the Prior Art
In the computer industry, circuit board components are continually being shrunk so that they can either be made to occupy less space on circuit boards or the boards constructed to contain more components and thus be more powerful. In both cases, there is continual pressure to shrink the size of the components, such as capacitors, resistors, etc., that are made a part of the circuitry. Long ago, in the shrinking process, some of these components lost their terminal wires so that many of them are now directly connected to the circuit board through soldering.
A typical capacitor chip is now about 0.060 inches long and 0.030 inches on a side. For processing the chips to be able to be later soldered directly onto a circuit board, each end of the chip must be metalized to a depth of about 0.012 inches. Large numbers of these chips may be subject to this metalization process using the apparatus described and claimed in U.S. Pat. No. 5,226,382 (the '382 patent). In this apparatus, an endless metal belt is used that contains a plurality of soft, rubbery masks that have individual holes formed in them into which the chips are individually loaded. The belt carries the chips through dobbing stations where a smear of a small amount of metalizing paste is placed on the ends thereof and then carries them through an oven to dry them. Subsequently, they are fired in a high temperature furnace to make the paste hard and capable of direct heat soldering onto a metalized landing formed on the circuit board.
In the apparatus of the '382 patent, an upright hollow load bowl or wheel, defined by an outer thin cylindrical metal wall, is mounted on a spindle driven by a stepper motor in a rotary motion. A series of orifices or passageways are formed in the cylindrical wall, preferably in a pattern matching the pattern of second apertures or openings in the rubber masks that are carried on the endless belt, and the passageways and openings are brought into alignment for a short time. The size of the opening in the metal bowl is slightly larger than the cross-section of the chip. An inventory of capacitor chips are maintained in the lower part of the load wheel. The wheel is subject to vibration or other such movement during its rotation about the spindle to urge the loose chips to drop into the passageways. The passageways may or may not have an angled lead-in opening transitioning from the inside surface of the cylindrical wall to the passageways themselves to aid in aligning chips for movement into the passageways. A chip retaining wall or surface is placed against the outside surface of the lower part of the load wheel to prevent the chips in the passageways from falling through. The mask in the endless belt is brought into alignment just as the load wheel passes out of contact with the chip retaining wall. A loading pin or pins, axially aligned above the passageways, then descends into the passageways to push the chips into the smaller holes in the resilient masks that are aligned therewith. The pins then are retracted from the passageways and the load wheel indexed to the next chip-filled holes and the process repeated.
A problem has arisen in the loading of the chips into the passageways. Due to the decreasing size of the chips, there is an increasing occurrence of chips becoming misaligned in the passageways. These chips are hard; the thin cylindrical wall of the load wheel does not have sufficient metal to resist deformity when one of these hard chips is forced askew into the passageway by the load pin. The result is usually a bent pin, a deformed passageway, or a crushed chip that interferes with later loading. While one or two of such instances is not that troublesome, continued creation of more damaged passageways will soon cause significant deterioration of the loading cycle.
While the size of the passageways can be reduced to improve initial alignment, filling begins to suffer and fewer passageways become filled with chips, thus decreasing overall output. A stronger load wheel could be manufactured to resist deformation, but this raises cost of operation.
A second problem comes about when the belt, and its masks, are changed for a new belt to handle a different size chip. The size of the holes in the new masks may be too small to receive the chip without undue pressure applied by the loading pins. This would result in crushed pins or torn masks. This could occur when the operator is unfamiliar with the new chip and its relation to the openings in the new belt and masks.